The present invention relates to a display device which utilizes emission of electrons into vacuum, and more particularly to a display device which enhances stable display characteristics by mounting cathode lines which have electron sources and control electrodes which control an electron pulling quantity (electron emission quantity) from the electron sources with high accuracy.
A color cathode ray tube has been popularly used conventionally as a display device which exhibits excellent properties such as high luminance and high definition. However, along with a demand for high image quality in recent information processing apparatuses and television broadcasting, a demand for a planar display (panel display) which is light-weighted and requires a small-space while ensuring properties such as high luminance and high definition is increasing.
As a typical example of such a planar display, a liquid crystal display device, a plasma display device and the like have been commercialized. Further, as the planar display device which can realize the high luminance, various types of panel-type display devices including a display device which makes use of emission of electrons from an electron source into vacuum (hereinafter, referred to as an electron emission type display device or a field emission type display device), an organic EL display which is characterized by its low power consumption and the like are expected to be commercialized soon.
Among such panel-type display devices, as the field emission type display device, a display device having an electron emission structure which is proposed by C. A. Spindt et al., a display device having a metal-insulator-metal (MIM) type electron emission structure, a display device having an electron emission structure which makes use of an electron emission phenomenon based on a quantum theory tunneling effect (also referred to as a surface conductive type electron source), a display device which makes use of an electron emission phenomenon possessed by a diamond film, a graphite film or a carbon nanotube and the like have been known.
The field emission type display device includes a back panel which forms cathode lines having field emission type electron sources and control electrodes on an inner surface thereof and a front panel which forms anodes and phosphors materials on an inner surface thereof which faces the back panel in an opposed manner, wherein the display device is constituted by laminating both panels while inserting a sealing frame between inner peripheries of both panels and by evacuating the inside thereof. Further, to hold a distance between the back panel and the front panel at a given value, distance holding members are provided between the back panel and the front panel.
FIG. 17 is a plan view of a back panel for explaining the schematic constitution of a field emission type display device. Here, FIG. 17 is constituted of a schematic view as viewed from a front panel side. With respect to the constitution which is explained in conjunction with the drawing, a technique which is relevant to fixing of control electrodes is the constitution which the applicant of the present invention has conceived in the process of reviewing the present invention and hence, the technique does not constitute a known technique. The back panel includes a plurality of cathode lines 2 having electron sources and a plurality of control electrodes 4 on a back substrate 1 which is preferably be made of glass, alumina or the like. A large number of cathode lines 2 extend in one direction and are arranged in parallel in another direction which crosses one direction on the back substrate 1. The cathode lines 2 are patterned by printing a conductive paste including silver or the like and cathode-line lead lines 20 are pulled to the outside of a sealing frame 9 from end portions of the cathode lines 2.
The control electrodes 4 shown in FIG. 17 are constituted of plate members which are manufactured as separate members. The control electrodes 4 are arranged above and close to the cathode lines 2 having the electron sources. A large number of control electrode 4 extend in the above-mentioned another direction and are arranged in parallel in the above-mentioned one direction. The control electrodes are explained as plate-like control electrodes 4 hereinafter. These plate-like control electrodes 4 are fixed to the back substrate 1 at fixing portions provided outside a display region AR using a pressing members 6 which are formed of an insulator such as a glass material. In the vicinity of the fixing portions, leads (plate-like control electrode leads) 50 are connected to the plate-like control electrodes 4 and are pulled out to the outside of the sealing frame 9. Pixels are formed on respective crossing portions between the cathode lines (electron sources provided to the cathode lines) 2 and the control electrodes 4. Here, the sealing frame 9 may be provided with a function of the pressing member 6.
An emission quantity (including ON and OFF) of electrons from the electron sources provided to the cathode lines 2 is controlled based on a potential difference between the cathode lines 2 and the control electrodes 4. On the other hand, the front panel not shown in the drawing includes anodes and phosphors on a front substrate which is made of a light-transmitting material such as glass. The phosphors are formed corresponding to the pixels formed at the crossing portions between the cathode lines 2 and the plate-like control electrodes 4.
The inside of the display device sealed by the sealing frame 9 is evacuated to a vacuum of 10xe2x88x925-10xe2x88x927 Torr, for example. Each crossing portion between the control electrode 4 and the cathode line 2 includes electron passing holes not shown in the drawing and these electron passing holes allow the electrons emitted from the electron source of the cathode line 2 to pass therethrough toward the anode side. The above-mentioned electron source is, for example, constituted of carbon nanotubes (CNT), diamond-like carbon (DLC) or other field emission cathode.
On the back substrate 1 on which the cathode lines 2 are formed, it is necessary to mount the plate-like control electrodes 4 at a given distance over the whole area of the display region AR with respect to the cathode lines 2. FIG. 18 is a plan view for explaining the shape of the plate-like control electrodes 4 as parts before mounting them on the back substrate 1. The structure of the plate-like control electrodes 4 shown in FIG. 18, the manufacturing method and the mounting method of the plate-like control electrodes 4, and the detailed structure of the plate-like control electrodes 4 are conceived by the applicant of the present application in the stage of reviewing the present invention and hence, they do not constitute known techniques. The plate-like control electrodes 4 are formed usually such that an aluminum-based or an iron-based thin plate is formed into a large number of stripe-shaped thin plates and a large number of electron passing holes are formed in these stripe-like thin plates by etching using a photolithography technique.
The plate-like control electrodes 4 which constitute parts are in a state that they are held by a frame 40. At the time of mounting the plate-like control electrodes 4 to the back substrate 1, the plate-like control electrodes 4 are positioned on the cathode lines 2 formed on the back substrate 1 together with the frame 40, and the outside of the display region AR is fixed by the pressing member 6 (FIG. 17). Thereafter, the frame 40 is cut and removed.
As explained in conjunction with FIG. 18, the plate-like control electrodes 4 are formed of thin plates formed by etching having a small thickness (approximately 0.05 mm) and hence, there exists a portion where a mechanical strength is sharply changed (a stress concentration portion to which a force is applied from outside) in the vicinity of a boundary region between a region where the electron passing holes are formed which is formed in the display region AR and the fixing portion formed of the pressing members 6 or the sealing frame 9. The mounting of the plate-like control electrodes 4 includes a step in which the pressing members 6 are fixed by applying a tension to the pressing member 6 in the extending direction (longitudinal direction) for ensuring a given distance between the cathode lines 2 and the plate-like control electrodes 4. In this step, cracks or breaking a reliable to occur in the plate-like control electrodes 4 so that the operability and the yield factor of products are degraded. Further, even with respect to a state of products after assembling, cracks may occur in the vicinity of the above-mentioned boundary region due to the repeated thermal expansion during the operation and the plate-like control electrodes 4 may break in an extreme case thus lowering the reliability of the products.
Accordingly, it is an object of the present invention to provide a display device which exhibits high reliability by preventing the occurrence of cracks and breaking of plate-like control electrodes 4 and by enhancing the operability at the time of assembling and the yield factor of products.
To achieve the above-mentioned object, the present invention provides the structure which prevents a sharp change of mechanical strength in the vicinity of a boundary between the display region of plate-like control electrodes and a fixing portion provided to a back panel to the plate-like control electrodes. Typical constitutions of the present invention are as follows.
(1). In a display device comprising a back substrate which has a plurality of cathode lines which extend in one direction, are arranged in parallel in another direction which crosses one direction and include electron sources respectively, and a plurality of control electrodes which cross the cathode lines in a non-contact manner within a display region, extend in another direction and are arranged in parallel in one direction on an inner surface thereof, and
a front substrate which has anodes and phosphors on an inner surface thereof and faces the back substrate with a given distance therebetween,
the control electrodes are formed of plate-like control electrodes, the plate-like control electrode includes electron passing holes which allow electrons emitted from the electron sources to pass therethrough in the display region, the plate-like control electrode has a portion which is fixed to the back substrate in an external non-display region, and the plate-like control electrode has a region where the strength of the plate-like control electrode is gradually changed toward an end portion thereof in the extending direction in at least a portion of the external non-display region.
(2). In the above-mentioned constitution (1), the plate-like control electrode has a region where the strength is gradually increased toward the end portion thereof in the extending direction.
(3). In the above-mentioned constitution (1) or (2), the strength of the plate-like control electrode is gradually increased from a boundary of the display region to a portion which is fixed to the back substrate.
(4). In any one of the above-mentioned constitutions (1) to (3), the strength of the plate-like control electrode is gradually increased from a portion which is fixed to the back substrate toward an end portion in the extending direction in the plate-like control electrode.
(5). In the above-mentioned constitution (1), the plate-like control electrode has the strength in the vicinity of a boundary of the display region which is substantially equal to the strength within the display region, and the strength is gradually increased from an intermediate portion of the external non-display region toward the end portion in the extending direction.
(6). In the above-mentioned constitution (1), the plate-like control electrode has the strength in a range from a boundary of the display region to a portion which is fixed to the back substrate which is substantially equal to the strength within the display region, and the strength is gradually increased outside the portion which is fixed to the back substrate toward the end portion in the extending direction.
(7). In any one of the above-mentioned constitutions (1) to (6), the plate-like control electrode has holes in at least a portion of the external non-display region.
(8). In any one of the above-mentioned constitutions (1) to (7), the plate-like control electrode has protrusions which protrude toward the back substrate side in the display region and the external non-display region.
(9). In any one of the above-mentioned constitutions (1) to (8), the plate-like control electrode includes a region where the width of the plate-like control electrode is gradually reduced toward the end portion in the extending direction in at least a portion of the external non-display region.
(10). In any one of the above-mentioned constitutions (1) to (9), the plate-like control electrode is fixed to the back substrate even within the display region.
(11). Ina display device comprising a back substrate which has a plurality of cathode lines which extend in one direction, are arranged in parallel in another direction which crosses one direction and include electron sources respectively, and a plurality of control electrodes which cross the cathode lines in a non-contact manner within a display region, extend in another direction and are arranged in parallel in one direction on an inner surface thereof, and
a front substrate which has anodes and phosphors on an inner surface thereof and faces the back substrate with a given distance therebetween,
the control electrodes are formed of plate-like control electrodes, the plate-like control electrode includes electron passing holes which allow electrons emitted from the electron sources to pass therethrough in the display region, the plate-like control electrode has a portion which is fixed to the back substrate in an external non-display region, and holes are formed in at least a portion of the external non-display region.
(12). In the above-mentioned constitution (11), the holes in the external non-display region are formed in a pattern which is substantially equal to a pattern of the electron passing holes formed within the display region.
(13). In the above-mentioned constitution (11), the holes in the external non-display region are formed over a substantially entire area of the external non-display region in a pattern substantially equal to a pattern of the electron passing holes formed within the display region.
(14). In the above-mentioned constitution (11), the plate-like control electrode has a region where pitches of the holes of the external non-display region are gradually increased toward an end portion in the extending direction of the plate-like control electrode.
(15). In the above-mentioned constitution (11), the holes of the external non-display region are formed in a pattern which is substantially equal to a pattern of the electron passing holes in the vicinity of a boundary of the display region and pitches of the holes are gradually increased toward an end portion in the extending direction of the plate-like control electrode from an intermediate portion of the external non-display region.
(16). In the above-mentioned constitution (11), the plate-like control electrode has a region where diameters of the holes of the external non-display region are gradually decreased toward an end portion in the extending direction of the plate-like control electrode.
(17). In the above-mentioned constitution (11), the holes of the external non-display region are formed in a pattern which is substantially equal to a pattern of the electron passing holes in the vicinity of a boundary of the display region and diameters of the holes are gradually decreased toward an end portion in the extending direction of the plate-like control electrode from an intermediate portion of the external non-display region.
(18). In the above-mentioned constitution (11), the plate-like control electrode has a region where pitches of the holes of the external non-display region are gradually increased toward an end portion in the extending direction of the plate-like control electrode, and
the plate-like control electrode has a region where diameters of the holes of the external non-display region are gradually decreased toward the end portion in the extending direction of the plate-like control electrode.
(19).In anyone of the above-mentioned constitutions (11) to (18), a pattern of the holes of the external non-display region is formed such that the holes are changed into non-penetrating recessed portion from an intermediate portion of the external non-display region toward an end portion in the extending direction of the plate-like control electrode.
(20). In any one of the above-mentioned constitutions (11) to (19), the plate-like control electrode is fixed to the back substrate even within the display region.
(21). In a display device comprising a back substrate which has a plurality of cathode lines which extend in one direction, are arranged in parallel in another direction which crosses one direction and include electron sources respectively, and a plurality of control electrodes which cross the cathode lines in a non-contact manner within a display region, extend in another direction and are arranged in parallel in one direction on an inner surface thereof, and
a front substrate which has anodes and phosphors on an inner surface thereof and faces the back substrate with a given distance therebetween,
the control electrodes are formed of plate-like control electrodes, the plate-like control electrode includes electron passing holes which allow electrons emitted from the electron sources to pass therethrough in the display region, the plate-like control electrode has a portion which is fixed to the back substrate in an external non-display region, and holes are formed in at least a portion of the external non-display region, the external non-display region has a region in which a width of the plate-like control electrode is gradually narrowed toward an end portion in the extending direction at least in a portion thereof.
(22). In the above-mentioned constitution (21), the plate-like control electrode has a region where diameters of the holes of the external non-display region are gradually decreased toward the end portion in the extending direction of the plate-like control electrode.
(23). In the above-mentioned constitution (21) or (22), the plate-like control electrode has a region in which the width of the plate-like control electrode is gradually decreased toward the end portion in the extending direction and a subsequent region in which the width of the plate-like control electrode is substantially fixed in at least a portion of the external non-display region.
(24). In any one of the above-mentioned constitutions (21) to (23), the plate-like control electrode is fixed to the back substrate even within the display region.
(25). In a display device comprising aback substrate which has a plurality of cathode lines which extend in one direction, are arranged in parallel in another direction which crosses one direction and include electron sources respectively, and a plurality of control electrodes which cross the cathode lines in a non-contact manner within a display region, extend in another direction and are arranged in parallel in one direction on an inner surface thereof, and
a front substrate which has anodes and phosphors on an inner surface thereof and faces the back substrate with a given distance therebetween,
the control electrodes are formed of plate-like control electrodes, the plate-like control electrode includes electron passing holes which allow electrons emitted from the electron sources to pass therethrough in the display region, includes a portion which is fixed to the back substrate in the external non-display region, and includes protrusions which protrude toward the back substrate side in the display region and in the external non-display region, and
at least in a portion of the external non-display region, the protrusions are formed such that a gap between the neighboring protrusions as measured in the extending direction toward an end portion in the extending direction of the plate-like control electrode is set substantially equal and an arrangement pitch in the extending direction is gradually increased.
(26). In a display device comprising a back substrate which has a plurality of cathode lines which extend in one direction, are arranged in parallel in another direction which crosses one direction and include electron sources respectively, and a plurality of control electrodes which cross the cathode lines in a non-contact manner within a display region, extend in another direction and are arranged in parallel in one direction on an inner surface thereof, and
a front substrate which has anodes and phosphors on an inner surface thereof and faces the back substrate with a given distance therebetween,
the control electrodes are formed of plate-like control electrodes, the plate-like control electrode includes electron passing holes which allow electrons emitted from the electron sources to pass therethrough in the display region, includes a portion which is fixed to the back substrate in the external non-display region, and includes protrusions which protrude toward the back substrate side in the display region and in the external non-display region, and
at least in a portion of the external non-display region, the protrusions are formed such that a gap between the neighboring protrusions as measured in the extending direction toward an end portion in the extending direction of the plate-like control electrode is gradually decreased and an arrangement pitch in the extending direction is set substantially the same.
(27). In a display device comprising a back substrate which has a plurality of cathode lines which extend in one direction, are arranged in parallel in another direction which crosses one direction and include electron sources respectively, and a plurality of control electrodes which cross the cathode lines in a non-contact manner within a display region, extend in another direction and are arranged in parallel in one direction on an inner surface thereof, and
a front substrate which has anodes and phosphors on an inner surface thereof and faces the back substrate with a given distance therebetween,
the control electrodes are formed of plate-like control electrodes, the plate-like control electrode includes electron passing holes which allow electrons emitted from the electron sources to pass therethrough in the display region, includes a portion which is fixed to the back substrate in the external non-display region, and includes protrusions which protrude toward the back substrate side in the display region and in the external non-display region, and
at least in a portion of the external non-display region, the protrusions are formed such that a gap between the neighboring protrusions as measured in the extending direction toward an end portion in the extending direction of the plate-like control electrode is gradually decreased and an arrangement pitch in the extending direction is gradually increased.
(28). In any one of the constitutions (25) to (27), the plate-like control electrode includes holes at least in a portion of the external non-display region.
(29). In any one of the constitutions (25) to (28), the plate-like control electrode has indented portions on the front substrate side at positions corresponding to the protrusions in the external non-display region.
(30). In any one of the constitutions (25) to (29), the plate-like control electrode is fixed to the back substrate even in the display region.
Due to the above-enumerated respective constitutions of the present invention, the sharp change of mechanical strength hardly occurs in the vicinity of the boundary of the display region and the fixing portion of the display device which uses the plate-like control electrodes whereby the occurrence of cracks and breaking is prevented, the operability of assembling is enhanced, the yield factor of products is enhanced thus producing the highly reliable display device.
It is needless to say that the present invention is not limited to the above-mentioned constitutions and constitutions of embodiments which are explained hereinafter and various modifications are conceivable without departing from the technical concept of the present invention.